1. Field of the Invention
The present invention relates to an anchoring device for fastening in a pre-drilled hole or recess in concrete or another substantially brittle material. Specifically, the present invention relates to expandable female material fasteners, which are designed to be inserted into a concrete bore and then expanded via the insertion of a complimentary threaded bolt or rod, wherein the device acts as an anchor in otherwise brittle concrete material.
The technology behind concrete anchors has changed little over time, but there is still room for improvement in this area. The basic idea behind most concrete fasteners is that they are placed within a pre-drilled bore in the concrete and are then expanded so that the fastener engages with the walls of the concrete and creates friction. This generated friction is what secures the fastener within the concrete and prevents it from moving. The differences among existing concrete fasteners relate mostly to the ways in which the fasteners are expanded once placed within the bore. The expansion is accomplished in many different ways and thus there are all types of concrete fasteners, such as wedge anchors, sleeve anchors, concrete screws, drop-in anchors, machine screw anchors, strikes anchors, hammer drive anchors, split drive anchors, and lag shields.
Many different types of concrete fasteners exist, but most utilize the same basic strategy of having a portion that is expanded by a rod or a wedge to engage against the walls of the bore. Other types of concrete fasteners utilize epoxy or some other type of bonding agent to secure a fastener within a concrete wall. However, both of the previous mechanical wedge and epoxy designs can lead to anchor slippage over time. For the mechanical wedge designs, the frictional force generated by the interaction between the anchor and the bore's walls is not sufficient to hold the anchor indefinitely. For the bonding agent designs, the chemicals can wear down over time, which renders the anchor useless.
The present invention provides a new and novel means for securing a fastener within a concrete bore. The present protrusion anchor assembly relies on the same basic idea of the mechanical wedge designs in increasing the volume of the fastener once it is placed within the pre-drilled bore. However, the present invention applies the principle in a different way. Rather than having separate portions that are pushed apart by a wedge or angled baffles that are pushed into the surrounding concrete, the present invention utilizes a plug to deploy a plurality of pins from the body of the anchor after it has been placed within the concrete bore. The pins are gradually deployed while the anchor body is simultaneously rotated, carving a groove or grooves out of the surrounding concrete bore. The fully extended pins rest within the grooves and cannot be pulled or pushed therefrom since the fully-extended pins create a larger cross-sectional area for the anchor than the cross-sectional area of the rest of the bore. Although the present protrusion anchor assembly is expansible, only a small portion of the device is expansible and no other such device cuts grooves into the surrounding bore to help secure the device.
2. Description of the Prior Art
Devices have been disclosed in the prior art that relate to concrete fasteners. These include devices that have been patented and published in patent application publications. These devices generally relate to female concrete anchors that are used with an inserted thread or bolt. The following is a list of devices deemed most relevant to the present disclosure, which are herein described for the purposes of highlighting and differentiating the unique aspects of the present invention, and further highlighting the drawbacks existing in the prior art.
One such device in the prior art is U.S. Pat. No. 3,943,817 to Mess, which discloses a split bolt used in combination with an insert. Mess has two segments with external threaded surfaces that are designed to radially space apart and engage with the complementary threaded insert member when a wedge portion is inserted between the segments. The wedge portion has multiple camming surfaces along its length that engage with corresponding surfaces on the internal face of the bolt segments, which creates a stronger wedge. Although both Mess and the present invention use insertable wedges to create an engagement between the concrete fastener and the concrete, Mess requires the bolt to be used to combination with an artificial threaded recess or bore, whereas the present concrete fastener directly engages with the concrete.
Another such device is U.S. Pat. No. 4,475,329 to Fischer, which discloses an expansible concrete anchor device with a bonding agent. The concrete anchor consists of a slotted portion with a central bore that is expanded to fit the hole into which it is inserted via the insertion of an expander pin. The central bore is then filled with the bonding agent, creating adhesion between the expander pin and the expansible anchor, in order to support the engagement between the walls of the expansible portion and the concrete. The present invention does not utilize any bonding agents and instead relies purely on mechanical force to generate the frictional force between the walls of the anchor and the concrete. Furthermore, the present device utilizes a security plug in order to ensure that the protrusion actuator is fully engaged after the anchor has been installed.
U.S. Pat. No. 4,917,552 to Crawford discloses a pin drive anchor device, whereby the anchor is inserted into a wall of a cavity and then a pin is driven through the central bore of the anchor to expand the sleeve portions so that they engage with the wall cavity. The present invention utilizes pins that extend into the surrounding concrete and carve out a portion in order to secure the anchor within the bore, rather than an expansible sleeve portion as in Crawford.
Another such device is U.S. Pat. No. 5,116,176 to Yousuke, which discloses an expansion anchor that is expanded by forcing a wedge plug through the central bore of the anchor. As the anchor expands, the peripheral angular edges of the anchor are forced into the surrounding material, preventing the anchor from being removable from the pre-drilled bore in the material. The present protrusion concrete anchor utilizes a plurality of pins that extend into the surrounding material in order to secure the anchor, rather than a peripheral angular edge. Furthermore, the present invention utilizes a security plug that may be installed into the anchor after the anchor has been secured within the concrete wall in order to keep the pins engaged with the surrounding concrete, regardless of the outside forces acting on the anchor.
Finally, U.S. Pat. No. 5,228,250 to Kesselman discloses a tamperproof anchor bolt device. Kesselman consists of a standard expandable anchoring means attached to a tamperproof nut assembly. The tamperproof nut assembly is designed such that when a pre-determined amount of torque is applied, the cap portion breaks off, leaving the anchor in its expanded position. The cap being broken off prevents the anchor from being removed and therefore prevents undesired tampering. The present invention is not specifically meant to address potential tampering, but is instead designed so that it is secured firmly enough that it cannot be easily removed by forces acting on the anchor, not other individuals.
The present invention provides an expandable concrete fastener device having three main portions. The anchor portion consists of an elongated, largely cylindrical body that has a plurality of pins that are driven into the surrounding rigid material by the protrusion actuator in order to secure the anchor therein. The anchor installation tool removably engages with the anchor portion and provides a rod for driving the protrusion actuator into the terminal end of the anchor portion and thereby extending the pins into the surrounding material. The security plug portion has a threaded end that engages with the complimentary threading in the anchor portion and an elongated rod portion that pushes against the protrusion actuator, thereby ensuring that the protrusion actuator remains locked in place. The anchor is placed into a pre-drilled bore within the concrete or other rigid material and then the installation tool rotates the entire anchor portion while extending the pins, thereby cutting a shelf in the surrounding concrete that secures the anchor within the bore.
It is submitted that the present invention substantially diverges in design elements from the prior art and consequently it is clear that there is a need in the art for an improvement to existing concrete fastener devices. In this regard the instant invention substantially fulfills these needs.